Understanding children’s food allergies

Emergency room doctors see it all the time: A panicked parent comes into the hospital with child in tow, fearing for the child’s life because he has eaten something to which he might be allergic.

Maybe it was some peanut butter, a shrimp, a bite of cheese, a slice of apple, some strawberry, or something made from wheat.

The child’s reaction may range from vomiting to difficulty breathing, shock to unconsciousness, or a mildly upset stomach or skin rash.

“As there is with all things, there are varying degrees of intensity. Food allergies can be unpredictable,” says Dr. John Dean, head of the division of allergy at BC Children’s Hospital.

About 600,000 Canadians —or two per cent of the population — live with severe, anaphylactic allergies. Many thousands more live with less severe

allergies, and even more live with varying degrees of food intolerances or sensitivities.

It can be difficult to navigate the sometimes blurry lines between anaphylactic allergies, other allergies and food sensitivities. And it’s natural for parents to fear the worst when their child eats something they’ve been told to avoid.

“But normally speaking, only a very few foods cause allergies,” Dean says.

Those foods are peanuts, tree nuts, milk, eggs, fish, shellfish and sometimes soy. With all of them, it’s the food’s protein that causes the allergy.

Many people with severe allergies will feel a reaction on their tongue the minute they put the offending food in their mouth. From there, the reaction can escalate to life-threatening or can remain mild, if uncomfortable.

Those diagnosed with anaphylactic allergies often carry — or keep close at hand — auto-injectors, which quickly deliver a single dose of medication to slow the onset of symptoms.

But if there is any distinguishable distress with functions relating to the airway, breathing or circulation, Dean says that person should immediately be taken to a hospital. “It doesn’t take much imagination to know when something is wrong,” he says.

However, if someone has an adverse reaction after eating an apple or peach, drinking a glass of red wine or eating a bowl of pasta, it’s more likely they’re suffering from either an oral allergy or food intolerance, rather than a life-threatening anaphylactic allergy.

“With raw apples, plums, cherries, peaches, carrots, celery — all those ones are enzyme labile. So you’ll get the itchy mouth and the itchy throat as it passes through, but the moment it gets into the stomach it’s destroyed. That’s known as the oral allergy syndrome,” Dean says. “It gets much much more complex beyond that.”

Food intolerance and hypersensitivities generally have nothing to do with the classic allergic system, Dean says. Something like celiac disease, for example, is an immune reaction to gluten, barley, rye, oats and wheat, but it does not express itself as an antibody, as most allergies do.

“The main symptoms of celiac disease are malabsorption, abdominal symptoms, and you can get some skin manifestations of it, but it’s primarily a gut disease,” he says.

In other words, if your child tests

positive for celiac disease, there is no need to rush her to hospital if she accidentally eats a cracker or takes a bite out of a croissant.

Dean emphasized the topic of allergy testing during his interview with The Vancouver Sun.

He noted that while many people seek out allergists for skin tests to identify any foods they or their children might be allergic to, those test results are not 100-per-cent reliable.

“So many people go to an allergist and come back with a lot of positive results,” Dean says.

But a positive result does not necessarily mean somebody is going to have an adverse reaction to that food.

“Perhaps the best example of that is two per cent of all children have a positive skin test to peanuts, but only one per cent get symptoms on ingestion,” Dean said. “So half of the skin tests you’ve got there are false positives.”

Of course, he doesn’t recommend challenging a positive result by feeding your child peanut butter, but he does note that a positive allergy result “has a very poor predictive value” as to whether someone is going to have a severe reaction to a food.

With milk and egg allergies, Dean says about 80 per cent of kids outgrow the allergy by the age of five. So it’s not unusual to find a kid who can drink a glass of milk along with a three-egg omelette and show no symptoms of an allergy.

Yet the same child might have a positive allergy test for years to come.

“The most useful thing about skin testing is a negative test, which really means you don’t have the classic allergies. You don’t have the antibody there,” Dean says.

“It’s rather like a gun without a trigger, it’s not going to fire. Whereas a gun with a trigger may fire or it may not.”

Allergies of all kinds have increased significantly in the past 20 years, but theories to explain the increase are as varied as the allergies themselves.

Most of the allergy increases have been documented in the populations of northern, developed countries, leading some researchers to believe the increase has something to do with

hygiene, or possibly vitamin D.

But Dean says there is no definitive explanation yet.

“It’s an area of major flux at the moment.”

aobrian@vancouversun.com

Foods most commonly associated with anaphylactic allergies:

• Peanuts

• Tree nuts

• Sesame seeds

• Fish

• Shellfish

• Milk

• Eggs

• Soy

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